Adjoint based noise minimization of a round supersonic jet

Abstract

Jets with complex shock-cell structures appear in numerous technological applications. The shock/shear-layer interaction emanates a broadband noise component. This may trigger the thin shear layer at the nozzle exit, forming a feedback loop which results in a discrete noise component called screech. Both components are undesirable from structural and environmental (cabin noise) points of view. Screech tones produce sound pressure levels of 160 dB and beyond. The focus of the present research project lies in the minimization of supersonic jet-noise and in particular in the minimization of jet-screech. Since screech - a phenomenon which is not yet understood in all details - seems to be affected by the presence of the jet-nozzle, a porous material will be added to the nozzle exit to suppress the feedback mechanism. Thus, to minimize the emanated noise. It is by no means clear how the shape an characteristic properties of the porous material should be. To this end, an optimization technique, based on adjoint methods will be applied to optimize the material with respect to the emanated noise.